The invention relates to an arrangement for cooling electrical subassemblies arranged in a housing, in particular for use in base stations of a mobile radio system or access network system.
During operation, technical devices produce waste heat, which leads to the device heating up. Since a technical device can ensure its functionality only within a restricted temperature range, arrangements for cooling this device are normally provided.
In electrically operated devices, the power loss of components and subassemblies through which current flows leads to heating. If such technical devices are not installed in protected, temperature-controlled rooms, during operation attention must be paid not only to the permissible temperature range of the electrical subassemblies but, at the same time, also to the possible temperature range of the environment of the technical device. Both temperature ranges have to be taken into account when dimensioning the arrangement for cooling. Standard components for a technical device have, for example, a permissible operating temperature range of from 0 to 70° C. Components of this type are used, for example, in base stations of a mobile radio system or access network system, but also in other technical devices, such as traffic control devices or supply devices. Moreover, adequate protection from dirt particles and penetrating moisture must be ensured for the electrical components and subassemblies, above all when they are used outside closed rooms, it being necessary to comply with the protection regulations in accordance with the specified IP classes.
In base stations according to the prior art, such as is disclosed, for example, by the earlier German patent application 19626778.1, the problem of cooling the electrical components and subassemblies, with simultaneous protection from dirt and moisture, beginning from a specific IP class, is solved by using two cooling circuits separated by an air/air heat exchanger. In this arrangement, the atmosphere and the air stream produced by one or more fans in the interior of the base station are separated completely from the external ambient atmosphere. However, the complicated construction of the base station, containing two cooling circuits, has a detrimental effect on the costs, the volume and the weight of the base station. This construction also has the disadvantage that the cooling arrangement only operates at and above a specific temperature drop between the atmosphere in the interior of the base station and the ambient atmosphere, as a result of which the temperature in the interior is always above the temperature of the ambient atmosphere. In this case, under certain circumstances it may occur that the upper limiting temperature (for example 70° C.) of individual components or subassemblies is exceeded if the temperature of the ambient atmosphere exceeds the corresponding limiting temperatures. In general, it is true that: ambient temperature+heat-exchanger temperature difference ΔT+internal heating !<component limiting temperature (e.g. 70° C.). In order to reduce the temperature difference ΔT needed for the cooling, a higher technical outlay is needed with a simultaneous increase in the volume of the base station or, alternatively, the use of so-called active cooling devices such as compressors, Peltier modules etc.